The WordPress logo was the first thing that came to my mind, I downloaded it from here (see the trademark policy for details on usage).

Changing the looks
Since everyone has different requirements in terms of looks, I will show how to make simple changes to the class file. Let’s assume we want to get rid of the logo and have a centered title (Memorandum) instead.

To Remove the logo simply delete the logo command. In fact, this works with all texMemo-specific commands. To add a title, however, we need to make a slight modification in the texMemo.cls file. First, open the class file with any text editor, ideally with your preferred LaTeX editor. Scroll all the way down to the last block (“% To, From, Subject Block”) and add the following code just before that:

{\begin{center}
\Large\bf
M\textsc{emorandum}
\end{center}}

It adds the word “Memorandum” as a centered title in bold small capitals. Save the class file. To see the result, use the sample code from the beginning and remove the \logo{} command.

Sample output of modified texMemo class.

The texMemo files can be downloaded as a compressed file from Rob’s website. The main file is the document-class: texMemo.cls. For illustration purposes, Rob provides some example tex-files with output.

The easiest solution is to move the class-file (texMemo.cls) to your document directory. Another possibility is to install it globally. See here for more details on how to install extra packages (including class-files).